Non-printing indicia ink



United States Patent NON-PRINTING INDICIA INK Thomas A. Sharp, Rowayton,and Frederick L. Jones, Noroton Heights, Conn., assignors to Sperry RandCorporation, New York, N.Y., a corporation of Betaware No Drawing.Application May 16, 1957 Serial No. 659,484

3 Claims. (Cl. 106-25) The invention relates to inks. More particularly,it relates to an ink which is suitable for use as a nonprinting indiciamedium on offset printing plates of the colloid type. i

On such type printing plates, there is usually present a coatingcharacterized by an inherently water-swellable nature, thischaracteristic being employed to repel greasy lithographic printing ink,thusenabling the coatings to constitute the non-printing portions oflithographic oilset printing plates. Upon these coatings, it iscustomary .to apply relatively hard grease receptive images which areinked to form printing portionsof the plates. L

In lithographic printing, two immiscible substances are constantly beingbrought together at the surface of the lithographic plate. Since it isnecessary on the one hand 'to maintain, at the image portions, arelatively heavy unemulsified ink body, and on the other hand, to re"plenish continually the water in the non-printing portions of the plateto replace that carried away as the 'plate makes an impression, theoperating range is relaof acidity supplement one another to controltheink handling function.

In US. Patent 2,532,866 to Toland et al., issued December 5, 1950, thereare disclosed examples of colloid coatings for offset printing whereinthere. are included polyvinyl alcohol or gelatin as the colloid materialand a water soluble dibasic acid such as oxalic, tartaric, succinic, orfumaric acid. In U.S. Patent 2,532,865 ,to Toland etal., issued December5, 1950, there is disclosed a colloid coating includingpolyvinylalcohol, oxalic acid and a melamine-formaldehyde resin. The resin, inthe presence of the oxalic acid, is cured to form hard waterirnperviousmasses distributed throughout the coating and especiallyatits surface.The coating thus presents, on the one hand, a-multiplicity of highlygrease-retentive anchor points to which a greasy typewritten image orcharacter may be very firmly attached; and on the other hand, tinyintermediate areas of water swollen colloid, which if first moistened,will hold Water and repel greasy ink subsequently applied against thesurface of the plate.

In utilizing an ofiset printing plate having a coating such as disclosedin the Toland et a1. patents referred to above, it has been found thatknown nonprinting indicia inks cause the plate in the area of theindicia markings to become sensitive to'the hydrophobic press inkresulting in the reproduction of theindicia markings on the print. It isbelieved that such sensitivity may be due to-two factors. One factor istheexcess curing or cross-linking of the polyvinyl alcohol due to theresidual acid in the v .roller or both. In the latter situation, the twosources 5 for .the curing to reacha plate whereby its swellable propertyis appreciably re-' duced with a consequent loss of ink rejecting power.The second factor is the interaction between. the residual acid in theplate and the components of the indicia ink.

Accordingly, it is the primary object of the present invention toprovide an improved non-printing ink for use as an indicia medium onoffset printing plates of the colloid type.

It is further intended to provide a non-printing ink for use as anindicia medium on offset printing plates of the colloid type whichpreserves the hydrophilic nature of the plate in the area of indiciaprinting thereby eliminating the tendency of the plate to becomesensitive to hydrophobic press ink in such area.

In accordance with the invention, there is provided a non-printing inkfor use with an offset printing plate of the colloid type comprising ahydrophilic plasticizer, a relatively cohesive film former, a coloringagent selected from the group consisting of inorganic pigments and watersoluble organic dyes and a relatively mild base which is substantiallyinsoluble in neutral and alkaline medium.

For a better understanding of the present invention, together with otherand further objects thereof, reference is had to the followingdescription and its scope will be pointed out in the appended claims.

In utilizing colloid type offset plates, as explained hereinabove, thepolyvinyl alcohol water swellable colloid may be modified by addingmelamine formaldehyde resin and a dibasic acid thereto, both of thesematerials being dispersedthroughout the coating. T he resin, in thepresence of this acidic material; is cured to form hard waterimperviousmasses distributed throughout the coating and especiaily at its surface.The coating thus presents both a multiplicity of highly grease-retentiveanchor points to which a greasy typewritten image or character maysurface of the plate.

In such coating, it is believed that the polyvinyl alcohol is probablyundergoing continuous curing due to the presence of unreactedmelamine-formaldehyde resin andfree .dibasic acid in the plate. However,there is a tendency stable point and the balance of the distribution ofgrease repellent and grease receptive areas in the plate isadvantageously maintained. Actually, the acid may even in time tend todisappear. How ever, when indicia ink is added, this balance is upset inthe plate and the curing of the polyvinyl alcohol tends to proceedfurther, i.e., further cross-linking of the polyvinyl alcohol occurswith the result that some of the grease repellent areas become sensitiveto hydrophobic press ink. In addition, another undesired phenomenon isthe interaction of the residual free acid in the plate and thecomponents of the ink (particularly in the case in which the color is aspirit-soluble dye, which has an inherently greasy nature.)

Accordingly, the salient point of the invention is the incorporationinto the non-printing ink of an alkaline component, which is normallysubstantially insoluble in neutral and alkaline medium. This alkalinecomponent, which may suitably be a salt consisting ofa relativelyelectropositive metal radical such as the alkaline earth metals and aweak acid radical such as the carbonate, phosphate, oxalate, tartrate,etc. ions,reverses the curing action, i.e., the hardening cross-linkingaction when the by causing some hydrolysis of the polyvinyl alcohol. Inthis manner, the tendency of the polyvinyl alcohol colloid to becomesensitive to hydrophobic press ink in invention may be performed at roomtemperatures.

is relatively non-volatile and whichmaintains a good water ,1,

balance between the atmosphere and the plate. Suitable materials for useas the plasticizer are polyhydric alcohols such as glycerine, diethyleneglycol, polyethylene glycols 200 through 600 and polypropylene glycol400.

The binder should be a cohesive film former that keeps the ink in placethereby preventing smudging, and a material that wets readily. Examplesof suitable film formers are dextrin, gum arabic, carboxymethylcellulose and polyvinyl alcohol.

The coloring agent may be an inorganic pigment or a, water soluble dye.Although some spirit soluble dyes may be used, they present thedisadvantage of being grease receptive. An example'of a suitableinorganic material is Ultramarine Blue which has an attractive bluecolor,

is nonreactive, and is hydrophilic. Suitable organic dyes,

of course, are' sulfonated dyes which are water but not, spirit soluble.

The filler should be a powdery insoluble material which lendsconsistency, texture and workability to the ink.

It is not necessary that the filler have hiding power,

that is, ability to diminish the intensity of color of the ink, but itis preferred that it be white or of light color.

Examples of suitable fillers are kaolins such as china clay,

attapulgite, fullers earth, and barium sulfate.

The whitening agent is primarily a material which does have good hidingpower. In addition, it should have good flow properties and impart auniform viscosity and an even spreadability to the ink. Suitableexamples of whitening agents are titanium'dioxide and zinc oxide.

The base, which is insoluble in alkaline medium, should be a relativelymild one, i.e., one which will provide a pH of from 8 to 9 in the finalcomposition. Suitable examples of such bases are carbonates, phosphates,oxalates, tartrates, etc.. of the alkaline earth metals and somemagnesium salts of these acids.

V '4 indicia medium on colloid-type offset printing plates did not printout at all in a run of 1,000 copies. 1

Example II The same mixture as that in Example I was made except thatthere was further added thereto parts by weight of titanium dioxide. Thesamebeneficial results were obtained except that the indicia markingswere of a much ligher blue color.

Example Ill An ink was made, as in the preceding examples, comprising 40parts by weight of glycerine, parts by weight of dextrin, 5 parts byweight of titanium dioxide, 20 parts by weight of Ultramarine Blue, 10parts by weight of calcium carbonate and 20 parts by weight of chinaclay. This ink was a little thicker than those of Examples I and II, butotherwise displayed the same advantageous properties.

. Example IV An ink was made as described comprising -40 parts by weightof glycerine, 5 parts by weight of Ultramarine Blue, 10 parts by weightof calcium carbonate, and parts by weight of china clay. This was anefiective nonprinting indicia ink with a relatively strong blue color.

Example V A non-printing indicia ink was made which comprised 40 partsby weight of glycerine, Sparts by weight of dextrin, 5 parts by weightof titanium dioxide, parts by weight of Ultramarine Blue, 5 parts byweight of 'calcium carbonate, and -parts by weight of china clay. Thiswas the most viscous ink of all the examples shown, V 1

but was workable and had the required properties.

While there have been described what are at present:

considered to be the preferred embodiments of this invention, it will beobvious to those skilled in the art that various changes andmodifications may be made thereinwithout departing from the invention,and it is, therefore, aimed to cover all such changes and modificationsas fall within the true spirit and scope of the invention.

What is claimed is:

1. For use with an offset printing plate, an anhydrous nonprintingindicia ink consisting essentially of the fol Theranges ofconcentrations of the different constituents in the ink composition,while not critical, should be chosen to provide an advantageous ink. Thefollowing ranges have been found to be suitable for a particularembodiment in accordance with the invention.

. Percent Glycerine 25-55 pextrin 10-20 Titanium dioxide 0-15Ultramarine Blue 10-30 Calcium carbonate 5-25 China clay 0-20 Thepreparation of the ink compositions of the present A preferable methodof preparation is to add the ingredients to the glycerine, stir theresulting slurry vigorously or with a mechanical stirrer and then runthe stirred mixture through a colloid dispersion mill until the desiredconsistency is attained.

, The following examples illustrate preferred embodiments of theinvention.

Example I I An ink was prepared in accordance with the above methodcontaining 29 parts by weight of glycerine, '5 parts by weight ofdextrin, 5 parts by Weight of Ultramarine Blue and 11 parts by weight ofcalcium carbonate. This ink had a pH of between 8 and9 and when used asan 2. For use with an ofiset printing plate of the colloid 7 type, ananhydrous non-printing indicia ink consisting essentially of ahydrophilic plasticizer selected from the group consisting of glycerine,diethylene glycols, polyethylene glycols, and a polypropylene glycol, afilm former selected from the group consisting of dextrin, gum arabic,caboxymethyl cellulose and polyvinyl alcohol, a coloring agent selectedfrom the group consisting of inorganic pigments andwater-soluble organicdyes, a weak acid salt having an alkaline component which is normallysubstantially insoluble in neutral and alkaline media having anionsselected from the group consisting of carbonate,

lowing proportions of ingredients by weights:

Percent.

Glycerine 25-35 Dextrin -10-.-20 Titanium dioxide 0-15 Ultramarine. Blue10-30 Calcium carbonate 5-25 China clay l 0-20 phosphate, oxalate andtartrate, a filler, and a whitening agent selected from the groupconsisting of titanium dioxide and zinc oxide, having thefollowingproportions by weight:

Percent Plasticizer 25-55 Film former 10-20 Filler 0-15 Coloring agent10-30 ggiAcid salt 3. In combination an ofiset printing plate of thecolloid type having a polyvinyl alcohol Water-soluble colloid with aresin and a dibasic acid dispersed therethrough, nonprinting indiciaformer on said plate, said non-printing indicia being formed of ananhydrous hydrophilic ink consisting essentially of the followingproportions of ingredients by weights:

Percent Glycerine 25-55 Dextrin 10-20 Titanium dioxide -15 UltramarineBlue 10-30 Calcium carbonate -25 China clay 0-20 References Cited in thefile of this patent UNITED STATES PATENTS 1,055,720 Deuvel Mar. 11, 19131,364,542 Browne Jan. 4, 1921 6 Fitzgerald Feb. 14, 1922 Serchi June 21,1927 Bruce May 5, 1931 Goedike Nov. 21, 1933 Rowell .Aug. 24, 1937 WoodJan. 16, 1940 Davis Sept. 25, 1945 Toland et a1. Dec. 5, 1950 WorthenDec. 19, 1950 Kramsky et al. Nov. 4, 1952 Yunker et al Oct. 23, 1956Chambers at al. Nov. 20, 1956 Chambers et al Ian. 13, 1959 FOREIGNPATENTS Italy 1929 OTHER REFERENCES Wolfe: Printing and Litho Inks (pub.1949, MacNair- Dorland, page 271).

1. FOR USE WITH AN OFFSET PRINTING PLATE, AN ANHYDROUS NONPRINTINGINDICIA INK CONSISTING ESSENTIALLY OF THE FOLLOWING PROPORTIONS OFINGREDIENTS BY WEIGHTS: PERCENT GLYCERINE ------------------ 25-35DEXTRIN -------------------- 10-20 TITANIUM DIOXIDE ----------- 0-15ULTRAMARINE BLUE ----------- 10-30 CALCIUM CARBONATE ---------- 5-25CHINA CLAY ----------------- 0-20